2 BioPharmaNet-DIMORFIPA, University of Bologna, Bologna, Italy; 3 IRET Foundation, Ozzano Emilia, Bologna, Italy; 4 Laboratory of Neuropathol- ogy, Department of Neurosciences, University of Parma, Parma, Italy. Contact e-mail: b.imbimbo@chiesigroup.com Background: CHF5074 is a new gamma-secretase modulator that after chronic administration has been shown to inhibit brain plaque deposition and to attenuate spatial and contextual memory deficits in adult transgenic Alzheimer’s disease (AD) mice. It is not known if the drug is still cognitively active in aged transgenic mice with massive plaque deposition. We evaluated the effects of chronic administration of CHF5074 on object recognition memory in 16-month old transgenic mice overexpressing the Swedish muta- tion of the human amyloid precursor protein. Methods: Six-month old trans- genic female mice (n ¼ 16-27 per genotype per treatment) were treated with standard, CHF5074- (125 and 375 ppm) or DAPT-medicated diet (375 ppm) for 10 months up 16 months of age. Wild-type aged-matched littermates re- ceived vehicle, CHF5074 (375 ppm) or DAPT (375 ppm). The test consisted in two 10-min habituation sessions in an open field arena, followed 24 h later by a 10-min training session in which the animal was allowed to explore two identical objects. After a retention interval of 4 h, the animal was returned to the arena in which two objects, one familiar and one novel object were placed. The time exploring objects over 10 min was recorded and analyzed using a videotracking software. The ‘‘recognition index’’, defined as the per- cent time exploring the new object over the total time spent to explore, was used for statistical analysis. Data were analyzed using two-way ANOVA. Results: Compared to vehicle-treated wild-type mice, vehicle-treated trans- genic animals showed a significantly lower recognition index (48.9 6 7.3% vs 64.1 6 5.0%, p ¼ 0.051). CHF5074 dose-dependently increased of the recognition index (62.2 6 5.4%, p ¼ 0.101 and 65.8 6 4.6%, p ¼ 0.031 after 125 ppm and 375 ppm, respectively). Compared to transgenic controls, DAPT (375 ppm) did not show significant effects on discrimination index (53.8 6 5.4%). In wild-type mice, neither CHF5074 (375 ppm) nor DAPT (375 ppm) produced significant effects on behavior compared to vehicle- treated animals. Conclusions: These data show that chronic treatment with CHF5074 dose-dependently improves non-spatial memory in aged trans- genic AD mice and support its development as potentially disease-modifying agent of AD. P3-472 ARYL ACYLAMIDASE ACTIVITYASSOCIATED WITH LOW MOLECULAR FORMS OF ACETYLCHOLINESTERASE IN THE ONSET OF ALZHEIMER’S DISEASE Rathanam Boopathy 1 , Venkatachalam Lakshmi 2 , Loganathan Chitra 2 , Saravanan Ponne 1 , Maria Salud Garcı ´a-Ayllo ´n 3,4 , 1 Department of Biotech- nology, Bharathiar University, Coimbatore, Tamilnadu, India; 2 Molecular Biology and Biotechnology Division, DRDO-BU Center for Life Sciences, Bharathiar University, Coimbatore, Tamilnadu, India; 3 Universidad Miguel Herna ´ ndez-CSIC, San Juan de Alicante, Spain; 4 Centro de Investigacio ´n Biome ´dica en Red Sobre, Madrid, Spain. Contact e-mail: boopathybiotech@ yahoo.com Background: Although acetylcholinesterase (AChE) exists in different mo- lecular forms, the low molecular weight forms (lmf) are the most abundant in Alzheimer’s disease (AD) brain plaques. Apart from the esterase activity, AChE exhibits the unique aryl acylamidase (AAA) activity in vitro. How- ever, the corresponding in vivo function remains largely unknown. Based on our recent data, we hypothesize a critical role for the AAA activity of AChE, in AD pathology. While it is well established that Ser200, His440, Glu327 is responsible for esterase catalytic triad, the active site for AAA is not yet clearly illustrated. Metal chelators (eg:1,10-phenanthroline) have been implicated to improve AD prognosis. Methods: i) Acetylcholinester- ase Levels in Alzheimer Plasma ii) AAA/esterase activity ratio of lmf- AChE iii) In silico docking with benzalkonium chloride, a distinct modula- tor of AAA over esterase (identified by in vitro studies) iv) 1,10-phenanthro- line action on AAA activity of lmf-AChE. v) Compare inhibitory effect of AAA activity of 1,10-phenanthroline and different AD drugs(tacrine, huper- zine, galanthamine) on lmf-AChE in vitro and in silico. Results: i)Signifi- cant increase in 78 kD AChE in the serum of human AD patients. ii)AAA/esterase activity ratio of lmf-AChE is significantly higher than in other molecular forms. This finding combined with abundance of lmf- AChE in brain and serum of human AD patients, points to the importance of AAA/esterase ratio in modulating onset of AD. The AAA levels associ- ated with lmf-AChE during embryonic brain development, closely parallels its level in AD brain. iii)In silico docking with benzalkonium chloride un- veiled the AAA active site to comprise of Ser226, His440, Glu199 where His440 being shared by both activities. The identification of an independent active site for AAA led us to investigate AAA catalytic site-specific inhibi- tor. iv)Identified the mechanistic action to involve irreversible binding to the AAA active site of lmf-AChE. v)Inhibitory effect of 1,10-phenanthroline on AAA activity of lmf-AChE was significantly comparable to those of tacrine, huperzine, galanthamine in vitro and in silico. Conclusions: These studies demonstrate the tremendous potential of 1,10-phenanthroline in specifically inhibiting the AAA activity lmf-AChE and elucidating its role as lead mol- ecule for drug discovery. These results necessitates future studies on possi- ble site-specific modification of this molecule for promising therapeutic alternative in AD patients. P3-473 A COMPARISON OF THE ADAS-COG AND COMPUTERIZED COGNITIVE TESTING (CNTB): COGNITIVE DOMAINS, RATER ERRORS, SAMPLE SIZE ESTIMATES AND POWER Amy E. Veroff, i3 Research, Cambridge, MA, USA. Contact e-mail: Amy. Veroff@i3research.com The ADAS-Cog requires clinical skill to administer and rate properly. De- spite comprehensive rater training, certification, and central monitoring, the inter-rater reliability (IRR) of the total score is impacted by the lower IRR of the global language items, which require specialized clinical skills, and raters make administration and scoring errors. Computerized batteries serve as expert systems which facilitate training and provide standardized administration and stimulus presentation, precise reaction time measure- ment, accurate scoring, and data are electronic, eliminating transcription er- rors. The ADAS-Cog is not a comprehensive cognitive battery, focussing only on the core cognitive impairments of AD. The Computerized Neuro- psychological Test Battery (CNTB), designed to comprehensively assess cognitive function, has been validated against the ADAS-Cog, and is sensi- tive to MCI and AD impairments. The EMEA has written guidance regard- ing the need for more comprehensive cognitive assessment in dementia clinical trials. For ADAS-Cog and CNTB the following are described and compared: cognitive domains, common rater errors (rater training and cen- tral monitoring data for multiple AD clinical trials, and CNTB module com- pletion data). Standard power calculations for the ADAS-Cog and the CNTB at an alpha level of p < 0.05 were carried out based upon published literature. Between- and within-subjects power curves were generated for the two tests. The CNTB assessed cognitive domains more comprehensively than the ADAS-Cog. Even highly experienced/trained/certified raters made errors administering and scoring the ADAS-Cog (2-3 queries per subject visit centrally monitored). The CNTB module completion rate was nearly perfect (>98% of >24,000 module administrations), and scoring is auto- mated, eliminating errors. Assuming 80% power the approximate respective sample sizes for the ADAS-Cog and CNTB scales were 80 and 64. The or- dinal relationship favoring CNTB was present within a range of 40-80% sta- tistical power by both within- and between-subjects analyses. The potential for ADAS-Cog operational variability even in skilled raters may increase outcome variability, obliging larger sample sizes. Use of a computerized battery provides a means of limiting variability and reducing sample size. The EMEA’s guidance recommends more comprehensive assessment of cognitive domains than the ADAS-Cog; the CNTB is an alternative to be considered. Poster Presentations P3 S592